A foundation plan shows a footing with reinforcement marked as '#5 @ 12" O.C.' What does this specification indicate?
Correct Answer
A) Number 5 rebar spaced 12 inches on center
#5 refers to number 5 rebar (5/8-inch diameter), and '@ 12" O.C.' means the bars are spaced 12 inches on center throughout the footing.
Why This Is the Correct Answer
The notation '#5 @ 12" O.C.' is standard construction terminology where the # symbol indicates rebar size number, not quantity. Number 5 rebar has a diameter of 5/8 inch. The '@' symbol means 'at' and 'O.C.' stands for 'on center,' which means the spacing is measured from the center of one bar to the center of the next bar. This creates a uniform 12-inch spacing pattern throughout the footing reinforcement.
Why the Other Options Are Wrong
Option B: 5/8-inch rebar with 12-inch overlap
This completely misunderstands the notation by interpreting '#5' as length (5-foot sections) rather than rebar size number. Rebar is typically sold in standard lengths and cut to fit, not specified in the reinforcement schedule this way.
Option C: 5-foot sections with 12-inch spacing
This interpretation incorrectly assumes the '#5' refers to quantity (5 pieces) rather than rebar size designation. The '12-inch depth' interpretation is also wrong since 'O.C.' specifically refers to spacing, not depth placement.
Option D: 5 pieces of rebar at 12-inch depth
This misinterprets both the rebar size and the spacing notation. While #5 rebar is indeed 5/8-inch diameter, the '12" O.C.' refers to center-to-center spacing, not overlap distance between bars.
Memory Technique
Think 'Number = Name, @ = At, O.C. = On Center' - so #5 @ 12" O.C. reads as 'Number 5 rebar at 12 inches on center spacing.'
Reference Hint
Florida Building Code, Chapter 19 - Concrete, or ACI 318 reinforcement tables for rebar sizing and spacing requirements
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